The controversy over Prime Minister Enda Kenny of Ireland, who supports narrow abortion rights legislation in his country, speaking at Boston College’s commencement took a dramatic turn Friday when the head of the Roman Catholic Archdiocese of Boston declared that he will not attend the ceremony.

The announcement from Cardinal Sean P. O’Malley upped the ante in a ­debate that earlier in the week had pitted BC against the Catholic Action League of Massachusetts, a group that opposes abortion rights and had strongly criticized the university for inviting Kenny.

The Irish legislation would permit abortions if there is a real and substantive threat to the mother’s life, including from suicide.

In a statement, O’Malley said US bishops have urged Catholic institutions not to honor government officials who “promote abortion” with their policies.

“Since the university has not withdrawn the invitation and because the Taoiseach [prime minister] has not seen fit to ­decline, I shall not attend the graduation,’’ O’Malley said. “It is my ardent hope that Boston College will work to redress the confusion, disappointment, and harm caused by not adhering to the bishops’ directives.’’

By tradition, the Boston archbishop delivers the final benediction at BC’s commencement each year. The university is scheduled to award Kenny an honorary doctor of laws degree at the ceremony, which will be held May 20 at Alumni Stadium.

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“I assure the graduates that they are in my prayers on this important day in their lives,” said Cardinal Sean P. O’Malley.

“Although I shall not be present to impart the final benediction, I assure the graduates that they are in my prayers on this important day in their lives,” O’Malley said. “I pray that their studies will prepare them to be heralds of the Church’s social gospel and ‘men and women for others,’ especially for the most vulnerable in our midst.”

Jack Dunn, a spokesman for BC, defended the college’s choice for the second time this week, saying Friday that Kenny was invited because of the school’s close ties to Ireland.

Dunn added in his statement that BC, as a Catholic university, “supports the church’s commitment to the life of the unborn.”

“Prime Minister Kenny has encouraged individuals to read the bill and his position statement, which reaffirms the constitutional prohibition on abortion in Ireland and attempts to clarify and regulate Ireland’s ­response to the ruling of the ­European Court of Human Rights,” Dunn said.

Kenny’s press aides did not return e-mails seeking comment Friday.

Dunn also said that BC ­respects O’Malley and regrets that he will not attend.

The head of the Catholic ­Action League praised O’Malley in a brief phone interview Friday.

“We’re delighted,” said C. J. Doyle, the group’s executive ­director. “We commend the cardinal for his forthright and ­unambiguous statement.”

Doyle, a BC alumnus, added that the controversy is “not the first scandal and betrayal [of church teachings] to afflict BC and probably won’t be the last.” He said that he hopes O’Malley will “perhaps contribute to the reform of that institution.”

In March, BC threatened to take disciplinary measures against a group of students who were distributing condoms from their dormitory rooms, calling the act a violation of the univeristy’s mission as a Catholic institution.

Last spring, Victoria Reggie Kennedy, the widow of the late Senator Edward M. Kennedy and an abortion rights supporter, spoke at the BC Law School commencement, despite protests from some Catholics.

The cardinal’s decision, while welcomed by the Action League, drew criticism from one student leader. Stephanie Rice, a BC senior and president of the College Democrats of Boston College, spoke out against O’Malley’s move to skip commencement.

“I am deeply disappointed that Cardinal O’Malley has chosen to politicize what should be a day of celebrating the four years of hard work and learning that I and my classmates have experienced at Boston College,” Rice said in a statement.

“In my time here at BC, we have been taught to respect and understand the value of a diversity of opinions, and I am proud that those values will be represented at our commencement ceremony by Prime Minister Kenny.”

Marty Walz, president and chief executive officer of the Planned Parenthood League of Massachusetts, called Kenny an “appropriate commencement speaker.”

Walz said, “It is disappointing that a measure to provide health care to a woman whose life is in danger would draw protest in Massachusetts.”

Catholic Irish bishops have spoken out against the pending legislation in their country, calling it morally unacceptable.

Bishop Brendan Leahy of Limerick said in a recent homily that “we need both to affirm our conviction that abortion is never the solution while at the same time relaunching ­Ireland’s care of mothers and babies,” according to a transcript of his remarks.

But Kenny has said the pending measure would clarify Ireland’s strict abortion laws, not alter them.

The conflict on Kenny’s invitation is not the first time there has been controversy involving BC and the archdiocese over commencement ceremonies.

Some members of the BC community clashed with Cardinal Bernard F. Law a decade earlier. In 2002, a number of students and faculty told the Globe that Law should not attend graduation, in light of the scrutiny he faced for his handling of the sexual abuse crisis.